a) Field of the Invention
The present invention relates to apparatus and method for automatically controlling a vehicular velocity of a vehicle which follows up a preceding vehicle running ahead of the vehicle if the preceding vehicle is present, maintaining an inter-vehicle distance to the preceding vehicle.
b) Description of the Related Art
A Japanese Patent Application First Publication No. Heisei 9-263160 published on Oct. 7, 1997 exemplifies a previously proposed automatic vehicular velocity controlling system.
In the disclosed vehicular velocity controlling system, such a cruise run control as to make the vehicular velocity coincident with a target vehicular velocity is carried out when an inter-vehicle distance between a preceding vehicle which is present ahead of the vehicle and the vehicle in which the vehicular velocity control system is equipped is equal to or wider than a constant value and such a follow-up run control as to maintain the inter-vehicle distance at the constant value is carried out when the inter-vehicle distance is narrower than the constant value.
When such a vehicular velocity control release condition is established as a brake pedal being depressed, as a manual clutch being depressed, as a release switch being operated, or as the vehicular velocity being equal to or lower than a controllable minimum vehicular velocity under one of the above-described control states, the vehicular velocity control is released.
However, in the previously proposed vehicular velocity controlling apparatus, the vehicular velocity control is released when the vehicular velocity control release condition such as a manipulation of the brake, a manipulation of the brake, a manipulation of the clutch, the operation of the release switch, or the vehicular velocity being equal to or lower than the controllable minimum vehicular velocity is established.
The other control release conditions may include such a case in which a select position of a vehicular automatic transmission is changed from a drive (D) range to a gear shift maintaining range such as a third-speed range (3rd range) or a second-speed range (2nd range) in order for a vehicular driver to determine that an acceleration or engine braking is demanded.
Suppose a case in which when a shift selection for the automatic transmission is carried out to transfer the gear-speed shift range such as 3rd range or 2nd range while the vehicular velocity control is effected, the vehicular velocity control is set to be released.
Hence, even in a case where the vehicular driver temporarily carries out the gear speed range shift operation, the vehicular velocity is released. Thereafter, it is necessary to set again the vehicular velocity control (function). This operation make the system troublesome whenever the temporary shift operation for the automatic transmission is carried out.
It is an object of the present invention to provide apparatus and method for automatically controlling a vehicular velocity for an automotive vehicle in which when a shift operation of a speed range in an automatic transmission occurs during the follow-up run control for the vehicle to follow up the preceding vehicle, with a vehicular behavior (motion) taken into consideration, a decision as to whether the follow-up run control should be released is made so that an unnecessary release is prevented and a re-setting operation can be omitted.
According to one aspect of the present invention, there is provided with an apparatus for automatically controlling a vehicular velocity for a vehicle, comprising: an inter-vehicle distance detector to detect an inter-vehicle distance of the vehicle to a preceding vehicle which is running ahead of the vehicle; a target vehicular velocity variation rate calculating section that calculates a target vehicular velocity variation rate to make the detected inter-vehicle distance substantially equal to a target inter-vehicle distance; an automatic vehicular velocity controlling section enabled to perform an automatic vehicular velocity control to maintain the target vehicular velocity variation rate calculated by the target vehicular velocity variation rate calculating section; a shift operation detector to detect whether a range selection by a vehicular driver occurs from a drive range to a gear speed maintaining range and vice versa; a vehicular motion predicting section that predicts a vehicular motion at the gear speed maintaining range when the shift operation detector detects that the range selection by the vehicular driver occurs from the drive range to the gear speed maintaining range; an automatic vehicular velocity control release determining section that determines whether the vehicular motion predicted by the vehicular motion predicting section falls within an allowable range when the shift operation detector detects that the range selection by the vehicular driver occurs from the drive range to the gear speed maintaining range; and an automatic vehicular velocity control releasing section that releases the automatic vehicular velocity control by the automatic vehicular velocity controlling section when the vehicular motion falls out of the allowable range but continues the automatic vehicular velocity control by the automatic vehicular velocity controlling section when the vehicular motion falls within the allowable range.
According to another aspect of the present invention, there is provided with a method for automatically controlling a vehicular velocity for a vehicle, comprising: detecting an inter-vehicle distance of the vehicle to a preceding vehicle which is running ahead of the vehicle; calculating a target vehicular velocity variation rate to make the detected inter-vehicle distance substantially equal to a target inter-vehicle distance; performing an automatic vehicular velocity control to maintain the target vehicular velocity variation rate; detecting whether a range selection by a vehicular driver occurs from a drive range to a gear speed maintaining range and vice versa; predicting a vehicular motion at the gear speed maintaining range when detecting that the range selection by the vehicular driver occurs from the drive range to the gear speed maintaining range; and determining whether the vehicular motion predicted falls within an allowable range when detecting that the range selection by the vehicular driver occurs from the drive range to the gear speed maintaining range; releasing the automatic vehicular velocity control in a case when the vehicular motion falls out of the allowable range; and continuing the automatic vehicular velocity control in a case when the vehicular motion falls within the allowable range.